1. Field of the Invention
The invention relates to a light-emitting diode lamp, and more particularly to a leadframe for a light-emitting diode lamp.
2. Description of the Related Art
Referring to FIG. 1, light-emitting diode lamp 1 comprises a packaging cup 11, a light-emitting diode chip 12 and a transparent encapsulant 13.
The packaging cup 11 comprises a leadframe 111 and a cup body 112. The leadframe 111 comprises two spaced apart conductive legs 113, each of which includes a base section 114, and a first extension section 115 extending from a bottom end of the base section 115 in a direction toward the other one of the conductive legs 113, and a second extension section 116 extending from a top end of the base section 115 in a direction toward the other one of the conductive legs 113. The conductive legs 113 are connected electrically and fixed to a conductive substrate 14 (as shown by the dotted lines) for connection with an external power source.
The cup body 112 encloses partially the leadframe 111 and exposes the bottom of the first extension sections 115 of the conductive legs 113 and the top of the second extension sections 116. The cup body 112 and the second extension sections 116 cooperate to define an encapsulant space adapted to fix the light-emitting diode chip 12 to one of the second extension sections 116. The light-emitting diode chip 12 is fixed to one of the second extension sections 116, and the encapsulant 13 is filled in the encapsulant space.
In operation, electric current flows from the conductive substrate 14 to the light-emitting diode chip 12 through the first extension sections 115, the base sections 114 and the second extension sections 116. Heat generated by the light-emitting diode chip 12 transfers from the respective second extension section 116 to the bottom of the first extension section 115 through the base section 114 and is then dissipated from the conductive substrate 14 to the environment.
Since the generated heat transfers along one of the second extension sections 116, to which the light-emitting diode chip 12 is fixed, in a direction away from another second extension 116 to reach the respective base section 114 and the respective first extension section 115 for final discharge to the environment, the path for heat transfer is long and the rate of heat transfer is slow resulting in accumulation of heat and reduction of the service life of the light-emitting diode chip 12. Moreover, due to the accumulated heat, the cup body 112 is prone to deform and change in its intrinsic properties, and can even release toxic gases as a result of chemical reaction caused by heat.